Programmed oil ignition



I 0a. 6, 1970 W S H ET AL 3,532,450

PROGRAMMED OIL IGNITION Filed Dec. 9, 196.8 2 Sheets-Sheet 1 FLAME FLAME sENsm INDICATING MEANS MEANS 22 24 CONTROL MEANS LOCKOUT MEAN 26 S FUEL l2 4 VALVE t 1 1$ fl IGNITION MOTOR TRANSFORMER SECONDS CAM FUNCTION'O 5 IO I5 20 5O 55 6O 58 BURNER MOTOR 6O OIL VALVE 6O HEAT RE LAY H0 I15 I20 62 TRIP RELAY 64 TIMER MOTOR INVENTORS ARDEN L4 MUNSON \JAN E s A. HIRSCH FM k ATTORNE United States Patent 3,532,450 PROGRAMMED OIL IGNITION James A. Hirsch and Arden L. Munson, Indianapolis,

Ind., assignors to P. R. Mallory & Co. Inc., Indianapolis, Ind., a corporation of Delaware Filed Dec. 9, 1968, Ser. No. 782,327 Int. Cl. F23n US. Cl. 43126 12 Claims ABSTRACT OF THE DISCLOSURE A fuel burning system utilizes a light sensitive means such as, for example, a photosensitive resistor as a flame sensing element. The system utilizes the photosensitive resistor in conjunction with a flame relay which is energized when there is no flame and deenergized when flame appears. The flame sensing-relay circuit is on the secondary (low voltage) side of the control transformer. The flame relay is in series with a trip relay to check the integrity of the circuit.

in present day modern fuel oil burning systems, very high pressures are used to vaporize the oil before it is ignited in order to develop a flame temperature which approaches that of natural gas. In many cases the oil is broken down to a particle size less than microns before ignition. Such systems require a carefully executed program for ignition, burning and purging. Also, if ignition is not obtained in a predetermined time, provisions must be made for deenergizing the system in a fail-safe condition.

Among the many elements of the control means used to carry out the executed program which can cause considerable difliculty is that of the means used to detect the presence or absence of a flame. It is essential that the flame used to promote the combustion of the fuel be present at various stages of the programming cycle. Also it is imperative that the flame be extinguished at the end of a particular burning cycle. A control means used to sense the presence or absence of a flame and to control the actuation of the programmed cycle from the coil ignition system generally includes a flame relay operating in conjunction with a heat relay. Prior to this invention, a conventional mode of operation in a flame sensing relay circuit, employing the flame relay and heat relay, was to energize the flame relay when there was a flame and to deenergize the flame relay when the flame was extinguished. With the control means for the flame operating in such a mode it was difficult to independently check the action of the flame relay and heat relay.

Another problem associated with the flame sensing relay circuit is that such circuit was normally connected on the primary (high voltage) side of the control transformer of the circuit for the fuel burning system. With the relay circuit so connected, component costs are significantly higher and wiring must be run in conduits.

Accordingly, it is an object of the present invention to provide a fuel burning system having a flame relay and a heat relay which can be independently checked.

Another object of the invention is to provide a control means for a fuel burning system having a flame indicating means including a flame relay wherein the flame relay is energized when there is no flame and deenergized when flame appears.

Another object of the present invention is to provide a ice fuel burning system having a flame indicating means that is on the low voltage side of the control transformer of the systems circuit.

Still another object of the invention is to provide a fuel burning system having a flame indicating means in series with a coil of a trip relay.

Yet another object of the invention is to provide a fuel burning system having a flame indicating means which is in series with the coil of a trip relay and this series circuit is in shunt with a heat relay.

Another object of the invention is to provide a three terminal lockout means.

A further object of the invention is to provide a fuel burning system wherein the flame indicating means is responsive to a flame sensing means.

Another object of the invention is to provide a flame sensing means which utilizes a photosensitive resistor to sense the presence or absence of a flame.

Still another object of the invention is to provide a flame sensing means utilizing a photosensitive resistor to deenergize a flame relay.

Yet still another object of the invention is to provide a flame indicating means including a flame relay which is operated by a solid-state circuit.

Other objects of the invention and the nature thereof will become apparent from the following description considered in conjunction with the accompanying drawings and wherein like reference numbers describe elements of a similar function.

For illustrative purposes, the invention will be described in conjunction with the accompanying drawings in which:

FIG. 1 is a block diagram showing the basic elements for the programmed ignition system of the present invention.

FIG. 2 is a schematic wiring diagram showing the circuit of the programmed ignition system of the present invention.

FIG. 3 is a time sequence chart of the programmed ignition system of the present invention.

Generally speaking, there is provided in fuel burning systems a control means including programming means for energizing burner operating means in a predetermined sequence; flame sensing and indicating means coupled to the control means, the indicating means being energized when there is no flame, and being deenergized when a flame appears, and a lockout means coupled with said control means and said indicating means for deenergizing the entire circuit. The flame indicating means is on the secondary side of the control transformer for the system in series with a coil of a trip relay. This series circuit is in shunt with a heat relay. The fact that the indicating means is energized when there is no flame, and deenergized when flame appears is contrary to the traditional mode of operation of fuel burning systems. But by reversing the action, the continuity of the lockout means and the flame sensing means is proved by the operation of the flame indicating means.

Referring now to FIG. 1, there is shown a block diagram showing the relationship of the basic elements of the present fuel burning system. As shown, a control means 10 is connected across a suitable AC power source indicated by L and L The control means includes a combination of devices which serve to operate burner operating means 12 in accordance with a programmed predetermined sequence. The burner operating means includes a motor 14, a fuel valve 16, and an ignition transformer 1. Coupled across the secondary or low voltage side of the circuit for the control means is a flame sensing means 22, a flame indicating means 24 and a lockout means 26. The flame sensing means indicates the presence or absence of a flame in the fuel burning system. Flame sensing means 22 causes flame indicating means 24 to be energized when there is no flame and when the low voltage is present. As will be hereinafter described, energizing the flame indicating means causes current to flow through the appropriate devices of the control means to cause burner operation in accordance with a predetermined programmed sequence. The lockout means 26 is energized momentarily during the energization of the indicating means 24, with operation of the indicating means causing the lockout means to be de-energized. Such momentary energization of the lockout means serves to keep the flame relay from being energized unless there is electrical continuity.

Referring now to FIG. 2 there is shown a wiring diagram for the present fuel burning system. The electrical input to the circuitry is provided by the input terminals L and L; which are connected to a suitable alternating current power source. L is connected to the contact 36 of the flame relay 34, and contacts 50 and 52 of the heat relay 41 and to the stationary switch contacts 54 and 56. L is connected to burner motor 14, oil valve 16, control transformer 28, ignition transformer 18 and timer motor 48. There is an ignition relay 46 connected between timer motor 48 and the ignition transformer 18 through fuse 44. Igniter relay 46 is also connected to contact 36 of flame relay 34. There are four cams, 58, 60, 62 and 64 mounted on a cam carrying shaft 48 so as to be rotated by motor 48. Burner motor 14 is energized by the closing of movable contact 66 in response to the rotation of cam 58. Cam 60 controls the movement of movable contact 68 which closes a circuit to either the oil valve 16 or the control transformer 28. Cam 62 controls the movement of movable contact 53 which alternately opens or closes an electrical circuit between transformer 28 and flame relay 34. Cam 64 biases movable contact 55 which opens and closes an electrical circuit between flame relay 34 and heat relay 41.

The circuit for the flame sensing means, flame indicating means and the lockout means is indicated generally at numeral 70. The: lockout means includes trip relay 38. Trip relay includes three terminals, one terminal for a contact of the relay, one terminal for its coil and another terminal common between the coil and the contact. Flame sensing means 22 is a suitable device which may be of a low voltage construction which responds to the flame by a substantial reduction of its resistance. It is here depicted by a photosensitive resistor 30. Various other similar devices, such as photosensitive semiconductors may also be used. The flame indicating means includes a silicon controlled rectifier 32 in series with flame relay 34. Also included as part of the flame indicating means are a diode 31 and resistor 33. The flame relay 34 is in series with lockout means 26 both of which are connected across the secondary side of transformer 38. Flame sensing means 22 is connected gate to cathode of SCR 32 which is biased by diode 31 which is in series with resistor 33 connected between flame relay 34 and lockout means 26-. A heat relay 41 is connected in series with thermostat 40 and switch 3? with the thermostat 40 being coupled to control transformer 28.

Referring now to FIGS. 2 and 3, the operation of the circuit as applied to fuel burning systems can be described. With the control deenergized and ready to ignite, the following state prevails. Timer contact 56' is closed thus energizing the transformer 28. The photocell 30 is dark, and therefore, its resistance is high. Resistor 33, diode 31 and the dark photocell form a voltage divider which provides suflicient power to the gate of the SCR 32 to trigger it into conduction to those alternations when the SCR anode is positive and thus the flame relay 34 is pulled in to energize or close its contacts 36- and 37. The trip relay coil 38, because it is in series with flame relay coil 34, had current flowing through it at the time that the flame relay was being operated. However, once flame relay contact 37 is closed, a short circuit is established around trip relay coil 38 via flame relay contact 37 and closed timer contacts 53 and 53', riding on cam 62, so that trip relay coil 38 is no longer energized.

All other timer contacts are open and all other relays are de-energized in the unoperated position.

When the contacts of thermostat 40 are closed, the heat relay 41 is operated. Such closing of the thermostat contact occurs when there is a demand for heat. One of the heat relay contacts energizes the ignition transformer 18 (or other ignition device) through the fuse 44 and the coil of the igniter relay 46. If the igniter is shorted out, the fuse 44 will blow. If the igniter current is too low (e.g. there is no spark), the igniter relay 46 will not op erate. But if conditions are right for ignition, the igniter relay will operate, energizing the timer motor 48.

The timer now sequences, opening contact 54 which shuts off burner motor 14. The timer continues to sequence opening contact 56'. Contact 56' is paralleled by the now closed contact of the heat relay 41, so the control transformer 28, heat relay 41 and flame relay 34 remain energized.

Before contact 56' opens, it is possible to terminate the cycle by opening the thermostat 40. If this is done, the system remains at rest. However, once timer contact 56 opens, opening the thermostat causes the heat relay 41 to drop out; therefore the ignition transformer 18 and control transformer 28 are deenergized and the flame relay 34 drops out. Consequently, the timer motor 48 continues to operate, being energized through the normally closed contacts of the flame relay and the heat relay until once again 56' closes, energizing the control transformer and causing the flame relay to pull in. The preceding applies at all times in the cycle when contact 56 is open and the thermostat is opened. It is noted that the burner motor 14 will operate during the remainder of the cycle, but the oil valve 16, switched in parallel with the control transformer 28, cannot operate once the thermostat contacts have opened until the timer passes through the at rest position and a new cycle begins.

Loss of power is equivalent to opening the thermostat 40. Once contact 56 has opened, loss of power will cause the heat relay 41 to move to its unoperated position, deenergizing the control transformer 28 and its related circuitry, and causing the timer to cycle to its at rest position before ignition is again attempted. This applies anywhere in the cycle where contact 56 is open.

The times assigned on the time chart of FIG. 3 are for the most part arbitrary, it being understood that a considerable tolerance could apply. According to the time chart, contact 56 opens at 4 seconds, contact 53' opens at 4 /2 seconds for one second. This checks the electrical integrity of the circuit prior to a try for fire. This is accomplished by putting trip relay 38 or lockout means 26 back in the circuit, that is, in series with flame relay 34 and SCR 32. If trip relay coil 38 is opened, flame relay 34 drops out and contact 36 transfers to shut off the timer motor and ignition transformer. Contact 53 closes at 5 /2 seconds, and contact 54' closes at 7 seconds. Contact 55' closes at 9 seconds. The action of contact 53 which will be discussed later, is the provision of a check mechanism. The closure of contact 54 energizes the burner motor 14, and that of contact 56' operates the oil valve 16. Such operation of the oil valve is indicated as being at from 15-60 seconds. That is, the oil valve can be operated at any given instant between the indicated time. In the sixty seconds that follow the opening of the oil valve 16, one of four things may occur: The thermostat 40 could be opened or the electrical power could be lost, both of which cases have already been covered. If neither of the above occur,

there may or may not be a flame which are the other two conditions.

First assume there is no flame. At 58 seconds contact 53 opens causing the trip relay contacts 39 to open, the trip relay being a suitable time-current integrating device such as a bimetallic actuated switch. At 60 seconds contact 56 opens tripping out the oil valve. When the trip relay operates it causes the flame relay to drop out which in turn removes power to the low voltage circuit. The low voltage holding path is through a contact 50 on the heat relay.

When the trip relay 38 does operate, the contact latches open the heat relay circuit. The contacts remain latched open until manually reset, and thus no more cycles of operation may be initiated until the reset button on the trip relay is depressed.

When the heat relay 41 drops out, the timer motor 48 is energized through the normally closed contacts of the heat relay and the flame relay thus returning the timer to the at rest position. At 116 seconds, by the timer, contact 53 closes. When, at 118 seconds, contact 54' opens, the burner motor 14 is deenergized. The burner motor will be both energized and deenergized by a dropping cam spring, a feature which assures the required contact life. At 90 seconds (which is the same as 0 seconds) contact 56 closes and since the SCR indicates no flame through photocell 30, the flame relay 34 pulls in through the coil 38, the coil is bypassed by contact 37 and 53 and the control is at rest. No further cycle may be initiated until the trip relay 38 is reset in the manner previously described and the thermostat contacts are. closed.

Of four things that could happen between 15 seconds and 60 seconds, the possibility that flame is detected has not been considered. When this happens, the light from the flames falls on the photocell and causes it to be of low resistance. The aforementioned voltage divider of resistor 33, diode 31 and the photocell now delivers insufficient power to the gate of the SCR 32. to trigger the SCR into conduction and the flame relay 34 drops out.

The dropping out of the flame relay causes the ignition transformer to be energized from contact That is, the dropping out of the flame relay causes the timer motor and ignition transformer circuit to be completed through switch 36 to contact 55'. The ignition transformer and timer motor 48 remain on until second 59 at which time contact 55' opens shutting off the ignition transformer 18 and stopping the timer motor. The condition of the control will remain the same, burning oil, until one of two things happen.

The thermostat contacts may be opened (or, equivalently, electrical power may be lost), deenergizing the heat relay 41 and causing the control to sequence back to the at rest position as previously outlined. The trip relay 38 will not operate and another thermostat contact closure will be sufficient to initiate another operating cycle. Alternately, flame may be lost. In such a circumstance, the photocell 30 will become dark, the SCR 32 will be triggered, and the flame relay will operate once again. The ignition transformer 18 and timer motor are again energized as the control again tries for fire. This time, however, the trip circuit is energized and the timer starts advancing. There is only 1 second allowed to reestablish flame. If this does not occur the previously described shut-down occurs with the operation of the trip relay 38 finally inhibiting the system from a further try for fire. When the cycle was initiated, the timer motor was energized through the contact on the igniter relay 46. This feature assured that the timer would not start into its cycle until the ignition means had been proven operative.

Thus there is described a fuel burning system wherein there is a positive check on the trip relay which deenergizes the entire system, the check being made prior to initiation of a cycle. This positive check is made through an indicating means responsive to a flame sensing means, the indicating means being energized when there is no flame and de-energized upon the presence of a flame. These features and others are recited in the appended claims.

What is claimed is:

1. In a fuel burning system involving the controlled ignition and combustion of a fuel, a control means including programming means for energizing burner operating means in a predetermined sequence, said control means responsive to flame sensing means and indicating means, said flame sensing means sensing the presence or absence of a flame in said fuel burning system, said flame sensing means energizing said flame indicating means when there is no flame, and de-energizing said indicating means upon the presence of a flame, said indicating means causing said control means to be energized according to said programmed sequence, and a lockout means coupled with said indicating means and said control means, said lockout means energized momentarily during energization of said indicating means, said momentary energization deenergizing the entire circuit of said system.

2. In a fuel burning system according to claim 1 wherein said flame indicating means includes a half-wave volt age supply in series with a flame relay.

3. In a fuel burning system according to claim 2 Wherein said half-wave voltage supply is a silicon controlled rectifier.

4. In a fuel burning system according to claim 1 wherein said flame indicating means includes a silicon controlled rectifier in series with a flame relay connected across the secondary side of a control transformer in series with said lockout means, and said series circuit is in shunt with a heat relay circuit.

5. In a fuel burning system according to claim 3 wherein said flame sensing means is connected gate to cathode of said silicon controlled rectifier, said silicon controlled rectifier biased by a diode which is in series with a resistor connected between said flame relay and said lockout means.

6. In a fuel burning system according to claim 4 wherein said heat relay circuit is a series connection of a heat relay, a thermostat, and said lockout means, said thermostat coupled between said heat relay and said control transformer.

7. In a fuel burning system according to claim 1 wherein said flame sensing means is a low voltage means responsive to said flame with a negative coeflicient of resistance.

8. In a fuel burning system according to claim 7 wherein said low voltage means includes a photosensitive resistor.

9. In a fuel burning system according to claim 1 wherein said lockout means includes a trip relay.

10. In a fuel burning system according to claim 9 wherein said trip relay includes three terminals, one terminal for a contact of said relay, one terminal for the coil of said relay, and another terminal common between said coil and said contact.

11. In a fuel burning system according to claim .10 wherein said coil and said contact is in series with said flame relay and said flame sensing means, and this series combination is connected across the secondary side of a control transformer.

12. In a fuel burning system of the type having a thermostat means for establishing a circuit condition for a predetermined temperature, a motor driven timer having a plurality of cam operated switches for controlling elements of said system, a means for igniting combustible material within said fuel burning system, a means for energizing said igniting means when said thermostat es tablishes said circuit condition, said energizing means being connected to said thermostat and to said igniting means, a means for starting said timer when said ignit ing means is in a predetermined state, said starting means 8 being coupled to said timer and to said igniting means, means being connected to and energized by said cam 0p a flame sensing means and a flame indicating means couerated switches. pled to said energizing means, said indicating means References Cited being energized when there is no flame and deenergized UNITED STATES PATENTS when a flame appears, and a lockout means for deen 5 3,143,162 8/1964, Graves et a1 erg1z1ng said fuel burnlng system if combustion does not 3 433 572 3/1969 Giuffrida occur after a predetermined time, said lockout means coupled across said flame indicating means and said en- CARROLL DORITY, Pflmafy EXaITllIleI ergizing means, and a means for admitting a combustible U5, C1,X R material to said fuel burning systems, said admitting 10 431-71 

